An E. coli histone-like protein, IHF, acts directly to allow the translation of a Lambda gene, cII. Our hypothesis is that it accomplishes this by altering the structure of the cII transcript so that it becomes accessible to ribosomes; an IHF binding site lies adjacent to the cII Shine-Dalgarno sequence. We wish to analyze this regulatory system by genetic and biochemical approaches. The former is facilitated by our construction of numerous cII gene and operon fusions; the latter by our establishment of coupled transcription-translation system which reflects the IHF requirement for cII expression. We plan also to probe the structure of cII mRNA. Finally, we offer selection protocols to isolate host mutants in which cII expression is IHF-independent; these mutants may display alterations in the other phenotypes caused by an IHF-mutation.